P0139
DTC P0136-P0139
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0136
- HO2S Circuit Sensor 2
DTC P0137
- HO2S Circuit Low Voltage Sensor 2
DTC P0138
- HO2S Circuit High Voltage Sensor 2
DTC P0139
- HO2S Circuit Slow Response Sensor 2
Diagnostic Fault Information
Typical Scan Tool Data
Circuit Description
The heated oxygen sensor (HO2S) sensor 2 circuit diagnostic monitors the voltage on the signal circuit of the post catalyst oxygen sensor. In order to control emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), a 3-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting the HC and the CO into harmless water vapor and carbon dioxide. The catalyst also reduces NOx by converting the NOx to nitrogen. The powertrain control module (PCM) has the ability to monitor this process using the heated oxygen sensors HO2S 1 and HO2S 2. The HO2S 1 produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the 3-way catalytic converter. The HO2S 2 produces an output signal which indicates the oxygen storage capacity of the catalyst. This in turn indicates the catalysts ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the HO2S 1 signal will be far more active than that produced by the HO2S 2.
Conditions for Running the DTC
P0136, P0137, P0138, or P0139
* DTC P0031, P0032, P0037, P0038, P0100, P0101, P0102, P0103, P0110, P0112, P0113, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0171, P0172, P0220, P0222, P0223, P0300-P0304, P0335, P0339, P0340, P0341, P0342, P0343, P0365, P0367, P0368, P0455, P0456, P0500, P0607, P2135, P2195, P2196, P2237, P2238, P2239, P2A00 are not set.
* The battery voltage is greater than 11 volts.
* The engine coolant temperature (ECT) is greater than or equal to 75°C (167°F).
* The engine speed is between 1,600-4,000 RPM.
* The engine is operating in Closed Loop fuel control.
* The DTCs run continuously when the above conditions are met.
P0137
The target air fuel ratio is RICH.
P0138
The target air fuel ratio is LEAN.
P0139
The engine is operating in fuel cut mode.
Conditions for Setting the DTC
P0136
* The average HO2S 2 voltage is greater than or equal to 600 mV.
OR
* The average HO2S 2 voltage is less than or equal to 250 mV.
P0137
The average HO2S 2 voltage is less than 250 mV for greater than 30 seconds.
P0138
The average HO2S 2 voltage is greater than 590 mV for greater than 30 seconds.
P0139
The HO2S 2 voltage is greater than 200 mV for greater than 1 second during engine decceleration, fuel cut mode.
Action Taken when the DTC Sets
DTCs P0136, P0137, P0138, and P0139 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0136, P0137, P0138, and P0139 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Important: To ensure the HO2S 2 is active, operate the engine at 2,000-2,500 RPM for 2 minutes, before performing the following verification.
1. Engine running at normal operating temperature and the exhaust system hot, observe the scan tool HO2S 2 voltage parameter. The reading should fluctuate between 250-650 mV.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the HO2S 2.
2. Ignition OFF, test for less than 10 ohm between the low reference circuit terminal 3 and ground G104.
• If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the PCM.
3. Ignition ON, observe the scan tool HO2S 2 voltage parameter. Verify the HO2S reading is between 35-55 mV.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.
4. Connect the test lamp between B+ and the HO2S 2 signal circuit terminal 4.
5. Ignition ON, verify the scan tool HO2S 2 voltage is greater than 1,125 mV.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
6. Verify that none of the following conditions exist:
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Alcohol/Contaminants-in-Fuel Diagnosis).
* Splits, kinks, or improper connections at the vacuum hoses
* The fuel system operating pressure is incorrect-Refer to Fuel System Diagnosis (Fuel System Diagnosis).
* The fuel injectors are operating lean or rich. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) (Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F)).
* Missing, restricted, or leaking exhaust components-Refer to Exhaust Leakage (Exhaust Leakage).
* Vacuum leaks at the intake manifold, manifold fittings, or throttle body - P0171
* Faulty crankcase ventilation system-Refer to Crankcase Ventilation System Inspection/Diagnosis (Testing and Inspection).
* A collapsed or restricted air intake duct and a restricted or dirty air filter - P0172
* Excessive fuel in the crankcase - P0172
* The incorrect operation of the evaporative emission control system-Refer to Evaporative Emission Control System Diagnosis (Evaporative Emission Control System Diagnosis).
7. Engine running at normal operating temperature, observe the scan tool HO2S 1 voltage parameters listed below while commanding the fuel injector rich or lean with the scan tool.
* Command the Fuel Injector Modification Commanded State to +25 percent - The HO2S 1 voltage should decrease to less than 3.0 V.
* Command the Fuel Injector Modification Commanded State to -11 percent - The HO2S 1 voltage parameter should increase to greater than 3.35 V.
* Command the Fuel Injector Modification Commanded State to 0 percent - The HO2S 1 voltage parameter should fluctuate between 3.2-3.4 V.
• If the scan tool HO2S 1 voltage parameter was not within the specified ranges, replace the HO2S 1.
8. If all the tests are normal, replace the HO2S 2.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Sensor 2 (Heated Oxygen Sensor Replacement - Sensor 2)
* Control Module References (Programming and Relearning) for control module replacement, setup, and programming